[Laser] Thoughts on receiver design

[Phil Lefever]

Hi all,

I'm finally getting around to building my LASER setup.
I am trying to nail down an adequate receiver design
for use with MCW using standard 670nm LASER diodes. My
receivers will be used at prime focus of 8" and larger
telescopes. My design goal is line of sight
communication over paths of 20+ miles primarily at
night.

I have been looking at the K3PGP and G0MRF designs.

The G0MRF design looks interesting and easy to build
based on the OPT301 sensor. The downside is the high
cost (~$45) of the sensor itself. The OPT101 is a lot
more cost effective although it appears to not be as
sensitive/low noise. Thoughts?

If I go the route of the K3PGP design what is the best
PIN diode sensor to choose? I have been looking into
the Photonics Detectors PDB-V107 as a possibility.
What are other people using with the 'PGP front end
design?

My transmitter will be modeled after the G0MRF design
initially starting with standard <5mw Red LASER
diodes.

One final question, is there any consensus at to
modulation frequency?

Since I plan on using a tight bandpass filter I'd like
to stay near a "standard" (if there is one) to be
compatible with others rigs. G0MRF uses 500Hz. My ear
prefers a bit higher frequency like 700Hz though.
There may be a electronic limit as to how fast the
LASER diode can be keyed as well. Any other comments?

73 & hope to _see_ you on the band ;)

Phil, KB0NES
EN34jt

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